Network event detection

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for identifying network events. In one aspect, a method includes monitoring signal characteristic values for signals transmitted over a communications channel of a power line communications system and determining that a signal level value for the channel is less than a threshold signal level value for the channel. In response to determining that the signal level value for the channel is less than the threshold signal level value for the channel, computing a signal to noise ratio for the communications channel and determining that the signal to noise ratio for the channel exceeds a threshold value. In response to determining that the signal to noise ratio for the communications channel exceeds the threshold value, storing data received over the communications channel as valid data.

BACKGROUND

This specification relates to detecting network events.

Service providers utilize distributed networks to provide services tocustomers over large geographic areas. For example, communicationscompanies utilize a distributed communications network to providecommunications services to customers. Similarly, power companies utilizea network of power lines and meters to provide power to customersthroughout a geographic region.

These service providers are dependent on proper operation of theirrespective networks to deliver services to the customers becauseoperational problems in the network can result in lost revenue for theservice provider. For example, the service provider may lose revenuebased on an inability to provide service during a network outage.Therefore, when a network outage or other network event that disruptsservice occurs, it is in the best interest of the service provider toidentify the cause of the problem and correct the problem as soon aspossible.

In many distributed networks, service providers first receive anindication that there is a problem with the network based on feedbackfrom customers. For example, customers may call the service provider toreport a network outage. Based on the information received from thecustomer, the service provider can take action to remedy the problemwith the network. For example, a service provider may access nodes inthe network to retrieve additional information regarding the status ofthe network and/or dispatch workers to attempt to identify the problem.

While a service provider can remedy network outages and other networkproblems by accessing nodes in the network and/or dispatching workers,the time and resources required to identify the cause of the outage orproblem can result in significant loss of revenue for the serviceprovider. Thus, if a service provider can reduce the time required toidentify whether a problem exists in a network, or even prevent theproblem before it occurs, the service provider can reduce lost revenuedue to network outages and increase customer satisfaction.

SUMMARY

In general, one aspect of the subject matter described in thisspecification can be embodied in methods that include the actions ofmonitoring signal characteristic values for signals transmitted over acommunications channel of a power line communications system anddetermining that a signal level value for the channel is less than athreshold signal level value for the channel. In response to determiningthat the signal level value for the channel is less than the thresholdsignal level value for the channel, computing a signal to noise ratiofor the communications channel and determining that the signal to noiseratio for the channel exceeds a threshold value. In response todetermining that the signal to noise ratio for the communicationschannel exceeds the threshold value, storing data received over thecommunications channel as valid data. Other implementations of thisaspect include corresponding systems, apparatus, and computer programs,configured to perform the actions of the methods, encoded on computerstorage devices.

These and other implementations can each optionally include one or moreof the following features. For example, methods can further include theactions computing baseline signal characteristics for each of thecommunications channels, the baseline signal characteristicsrepresenting normal operating characteristics for the channels; andspecifying the threshold signal level for the channel based on abaseline signal level.

Computing baseline signal characteristics for each of the communicationschannels can include computing, for each of the communications channels,a baseline signal level of the channel based on signal level values thathave been measured for the channel over a specified time. Monitoringsignal characteristic values for signals transmitted over the channelcan include monitoring signal characteristic values for a signalstransmitted over a channel of a power line communications system.

In response to determining that the signal level value for the channelis less than the threshold signal level value and that the signal tonoise ratio for the channel is greater than the threshold signal tonoise ratio methods can further include the actions determining that acapacitor bank has been activated in the power distribution system; andproviding a notification that the capacitor bank has been activated inthe power line distribution system.

Monitoring signal characteristic values can include monitoring signallevel values and noise floor measures for signals transmitted over thechannel. Determining that a signal level value for the channel is lessthan a threshold signal level value comprises detecting a signalamplitude for signals transmitted over the channel that are at leastfifty percent less than a baseline signal level for the channel.

Particular implementations of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. Signal anomalies resulting from significantnetwork events that may have been identified as outages can be moreaccurately. Activation of capacitor banks in a power distribution systemcan be distinguished from a power outage based on channelcharacteristics of communications channels in the system. A notificationthat a capacitor bank has been activated in the power distributionsystem can be provided, for example to a power provider that manages thenetwork, a maintenance staff, and/or a customer service staff thatreceives calls from customers to prevent repair crews from beingdeployed to investigate whether a power outage has occurred. Eventdetection can be continuously monitored and network events can beverified. More valid data can be stored by identifying a capacitor bankactivation as such rather identifying the activation as an outage.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other features, aspects, andadvantages of the subject matter will become apparent from thedescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example network environment.

FIG. 2 is a graph of an example signal for a channel in a PLC systemaffected by activation of a capacitor bank.

FIG. 3 is a flow chart of an example process for determining whether tostore data received over a channel.

FIG. 4 is block diagram of an example process for identifying activationof a capacitor bank in a power distribution system

FIG. 5 is a block diagram of an example computer system that can be usedto facilitate network event detection.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

A status subsystem monitors channel characteristics of communicationschannels in a network and identifies network event based on themonitored channel characteristics. The status subsystem can distinguishbetween a power outage and activation of a capacitor bank in a powerdistribution system based on the channel characteristics. In turn, thestatus subsystem updates the status of the channel and conditionallystores data received over the channel based on the status.

FIG. 1 is a block diagram of an example network environment 100. Thenetwork environment 100 includes a service network 101 in which aplurality of nodes 102 are coupled to a consolidator 104. The nodes 102can be any device capable of transmitting information in the networkenvironment 100. For example, the nodes 102 can be meters in a utilitynetwork, computing devices, television set top terminals or telephonesthat transmit data in the service network. The description that followsrefers to the nodes 102 as meters in a power distribution network.However, the description is applicable to other types of nodes 102 inother utility networks or other networks.

The nodes 102 can be implemented to monitor and report various operatingcharacteristics of the service network 101. For example, in a powerdistribution network, meters can monitor characteristics related topower usage in the network. Example characteristics related to powerusage in the network include average or total power consumption, powersurges, power drops and load changes among other characteristics.

The nodes 102 report the operating characteristics of the network overcommunications channels. Communications channels are portions of radiofrequency spectrum over which data are transmitted. The frequencyspectrum and bandwidth of each communications channel can depend on thecommunications system in which they are implemented. For example,communications channels for utility meters (e.g., power, gas and/orwater meters) can be implemented in power line communication (PLC)systems and wireless communications systems such as cellularcommunications systems, wireless broadband networks, wireless meshnetworks and other wireless communications systems.

Communications channels for each of these different communicationssystems have distinct operating parameters that are defined, in part, bycommunications standards and/or environmental considerations. Forexample, in a PLC system, operating parameters for communicationschannels are defined so that the communications channels can operate onthe same transmission lines on which power is distributed throughout apower grid. The description that follows refers to communicationschannels of PLC systems for example purposes. However, the descriptionis also applicable to communications channels in other communicationssystems.

In some implementations, the nodes 102 transmit the operatingcharacteristics of the distributed network 101 over communicationschannels to a consolidator 104. The consolidator 104 is a processingapparatus that consolidates communications from nodes 102 fortransmission though a data network 110. For example, the consolidator104 can receive data bits or data packets 106 from nodes 102 andgenerate a consolidated packet 108 that includes data from multiple datapackets 106 received from the nodes 102. While consolidated packets 108are discussed for example purposes, the consolidator 104 can operate asa repeater to retransmit the data packets 106 through the data network110 instead of creating a consolidated packet 108.

The consolidated packets can be generated such that redundant data inthe data packets is removed to increase efficiency. Similarly, aconsolidator 104 can re-format data received from the nodes 102 fortransmission to a device through a data network 110. For example, whenmultiple nodes 102 are all reporting the same network event (e.g., aservice outage), the consolidator can create a consolidated packet thatincludes a single instance of network event data identifying the networkevent and include data identifying each node that is reporting theevent. Thus, each consolidated packet can include data from manydifferent nodes 102 and transmitted over many different communicationschannels.

A consolidator 104 can be implemented as a node 102, a repeater, arouter or any other data processing device that can receive data fromnodes 102 and retransmit the data through a network environment 100. Insome implementations, a single consolidator 104 can receive data packets106 from thousands of nodes 102 and transmit the data packets 106 and/orconsolidated packets 108 through a data network 110.

The data network 110 can be a wide area network (WAN), local areanetwork (LAN), the Internet, or any other communications network. Thedata network 110 can be implemented as a wired or wireless network.Wired networks can include any media-constrained networks including, butnot limited to, networks implemented using metallic wire conductors,fiber optic materials, or waveguides. Wireless networks include allfree-space propagation networks including, but not limited to, networksimplemented using radio wave and free-space optical networks. While onlyone consolidator 104 is shown, the service network 101 can include manydifferent consolidators 104 to couple many thousands of nodes to thedata network 110.

In some implementations, the data network 110 couples the consolidator104 to a network management system 112. The network management system112 is a system that monitors and/or controls the service network 101.The network management system 112 can control different characteristicsof the service network 101 based on data received from nodes 102 thatare installed in the service network 101.

For example, in a PLC network, the network management system 112 canreceive a consolidated packet 108 that includes data indicating thatpower usage is significantly higher in a particular portion of a powernetwork than in other portions of the power network. Based on this data,the network management system 112 can allocate additional resources tothat particular portion of the network (i.e., load balance) or providestatus data specifying that there is increased power usage in theparticular portion of the power network.

The network management system 112 can provide the status data to a userdevice 120 that can be accessed, for example, by the network operator,maintenance personnel and/or customers. For example, status dataidentifying the detected increased usage described above can be providedto a user device 120 accessible by the network operator, who can, inturn, determine an appropriate action regarding the increased usage.Similarly, if the status data indicates that there is a network outage,the network management system 112 can provide data to user devices 120accessible by customers to provide information regarding the existenceof the outage and potentially provide information estimating a durationof the outage.

Data packets 106 and/or consolidated packets 108 may be transmitted overone of thousands of channels in a PLC system. However, the ability toreliably receive data over the channels in the PLC system can beaffected by significant network events that cause signal anomalies onthe communications channels. For example, when a power outage occurs ina PLC network, amplitudes of communications signals that are transmittedon channels over which nodes affected by the power outage communicatecan drop to substantially zero. Amplitudes of communications signals canbe measured in units of voltage or power and are referred to throughoutthis document as signal levels.

As the signal levels of signals transmitted over affected channelsapproach zero, data received over the affected channels may beunreliable. Therefore, some network operators will specify that at leasta threshold signal level that must be present on a channel for datareceived over the channel to be logged as valid data. Valid data can bestored, for example, to a data store, such as the channel data store116.

Each channel in the network can have unique operating characteristics,such that the threshold signal level specified for each channel maydiffer. For example, a first channel may have a center frequency thatcorresponds to an RF frequency for which signals through the PLC aresignificantly attenuated relative to other channels in the system. Thus,the signal level on the first channel may be consistently lower than thesignal level of the other channels, even in a normal operatingcondition.

Similarly, a noise floor for the first channel can vary relative to thenoise floors of other channels, such that absolute measures of signallevel reduction will have different effects on the reliability of dataon each of the channels. For example, data received over a channelhaving a higher noise floor than other channels can become unreliablefrom lower signal level reductions than the signal level reductions thatrender data unreliable on the other channels having lower noise floors.The noise floor of a channel as used throughout this document refers toa measure of the signals from noise sources that are present on thechannel.

The differences in channel characteristics for different channels can bea result of operating characteristics of components used to implementthe system and/or environmental factors. For example, gain and noisecharacteristics for a transmitter can vary over its radio frequencyoperating range such that signals transmitted at one frequency can havedifferent gain and noise characteristics than signals transmitted atanother frequency. Similarly, the environment in which the signals aretransmitted can affect channel characteristics. For example, othersignals being transmitted near the PLC system can interfere with signalsbeing transmitted in the PLC system and degrade the channelcharacteristics.

The channel characteristics include signal characteristics for signalsthat are transmitted over the channel. Channel characteristics for eachchannel can be measured, for example, by receivers that are receivingcommunications over the channels. For example, the consolidator 104 canmeasure RF characteristics (e.g., signal level and noise floor) for thechannels over which the consolidator receives data. The channelcharacteristics can be stored, for example, in a data store such as thechannel data store 116.

In some implementations, the channel characteristics are measured over aperiod of time to determine baseline channel characteristics for eachchannel. For example, the network management system 112 can receive datarepresenting measured RF characteristics of each channel for a specifiedperiod of time and compute baseline channel characteristics based on thereceived data. Baseline channel characteristics are characteristics ofthe channel when the channel is in a “normal” operating condition.Channels that are operating in a “normal” operating condition arereferred to as channels that are in a permanent state.

The baseline channel characteristics can include, for example, abaseline noise floor measure for the channel and a baseline signal levelmeasure. Each baseline characteristic (e.g., signal level and noisefloor) can be computed as a function of the corresponding channelcharacteristic measurements or computed based on statistical analysis ofthe corresponding channel characteristic measurements.

For example, the baseline signal level for a channel can be an average(or median or some other central tendency) value of the signal levelvalues that have been measured for the channel over the previous day,week, or month. Similarly, a baseline noise floor for a channel can bean average noise floor for the channel computed from the noise floormeasurements for the channel over a previous day, week, or month. Otherbaseline channel characteristics can also be computed, such as abaseline signal to noise ratio and/or a baseline data integrity measure(e.g., baseline bit-error-rate).

Using the baseline channel characteristics a threshold signal level canbe specified for each channel. The threshold signal level is a minimumsignal level (i.e., minimum signal amplitude) at which data receivedover the channel is assumed to be valid data. The threshold signal levelcan be a specified fraction of the baseline signal level, a specifiedabsolute signal level, or another specified measure of signal levelrelative to the baseline signal level.

The network management system 112 includes a status subsystem 114 thatuses the threshold signal levels to determine the status of each channelin the system. For example, the status subsystem 114 can continually orperiodically monitor the signal level on each channel and compare it tothe threshold signal level for that channel. When the signal level onthe channel remains above the threshold signal level, the statussubsystem 114 identifies the channel as being in a permanent state,thereby indicating that the data being received over the channel can bestored to the channel data store 116 as valid data. If the signal levelon a channel drops below the threshold signal level, the channel isidentified as being in a lost state, thereby indicating that the databeing received over the channel is not eligible to be stored in thechannel data store as valid data.

While the status subsystem 114 can identify a channel as being in apermanent or lost state based on the signal level of a channel, and inturn, an indication of the reliability of data being received on achannel, there are network events other than power outages that cancause the signal level of a channel to drop below the threshold signallevel. During some of these network events the data being received overthe channel may still be reliable data such that the data can be storedin the channel data store 116 as valid data.

Capacitor bank switching is an example of a network event in which datacan still be stored as valid data even though the capacitor bankswitching can cause signal levels of affected channels to drop below thethreshold signal level. A capacitor bank can be used in a powerdistribution network to regulate the power factor of the network. Forexample, when the power factor of a network begins to drop (e.g., basedon a load change in the network), a capacitor bank can be activated toincrease the power factor.

When the capacitor bank is activated, PLC signals being transmittedthrough channels affected by the activation can fall below the thresholdsignal level. Therefore, if the status subsystem is identifying channelstates based only on the signal levels of the channel, it may identifythe affected channels as being in a lost state. Thus, data received overthe channel while the signal level remains less than the thresholdsignal level will not be stored to the channel data store as valid dataand may be lost.

To prevent data loss on channels over which valid data is beingreceived, the status subsystem 114 is configured to determine the stateof a channel based on a signal to noise ratio for the channel when thesignal level for the channel falls below the threshold signal value. Forexample, in response to determining that a signal level for a channelhas fallen below the threshold signal level, the status subsystem 114can compute a signal to noise ratio for the channel and compare thecomputed signal to noise ratio to a threshold signal to noise ratio. Ifthe computed signal to noise ratio meets or exceeds the threshold signalto noise ratio, the status subsystem 114 can identify the channel asbeing in a permanent state, such that data received over the channelcontinues to be stored to the channel data store 116. However, if thecomputed signal to noise ratio is below the threshold signal to noiseratio, the status subsystem 114 can identify the channel as being in alost state, such that data received over the channel is not stored tothe channel data store 116.

In some implementations, the signal to noise ratio for each channel cancontinuously be computed, so that the status of the channels can becontinuously updated based on a comparison of the signal level to thethreshold signal level and a comparison of the signal to noise ratio tothe threshold signal to noise ratio.

FIG. 2 is a graph 200 of an example signal 202 for a channel in a PLCsystem affected by activation of a capacitor bank at time T1. The signallevel of the monitored signal 202 is plotted over time, which isrepresented by the x-axis of the chart 200. As described above, thebaseline level 204 for the channel can be determined and specified basedon previous measurements of the signal. The signal 202 has a signallevel that is less than the baseline level 206 at time T1, whichcorresponds to a time at which a capacitor bank is activated. However,the signal level for the signal 202 remains above the threshold signallevel until time T2. Therefore, from time T0 to time T2, the statussubsystem of FIG. 1 identifies the channel as being in a permanent statebased on the signal level and data received over the channel cancontinue to be stored.

At time T2, the signal level value for the signal 202 falls below thethreshold signal level 204 for the channel over which the signal 202 istransmitted. The signal level remains below the threshold signal level204 until time T3, which corresponds to the capacitor bank beingdeactivated. After time T3, the signal level value remains above thethreshold signal level. Therefore, after time T3, the status subsystem114 determines that the channel is in a permanent state based on thesignal level of the channel.

From time T2 to time T3, corresponding to the time from which thecapacitor bank was activated to the time at which the capacitor bank wasdeactivated, the status subsystem 114 may incorrectly identify thechannel as being in a lost state, for example, if the state of thechannel is determined based only on the signal level. However, thestatus subsystem 114 determines the signal to noise ratio for thechannel, and if the signal to noise ratio for the channel meets orexceeds the threshold signal to noise ratio, the status subsystem 114identifies the channel over which the signal 202 is received as being ina permanent state, rather than a lost state. In turn, data that wouldhave been otherwise lost due to an improper determination of the stateof the channel is stored as valid data when the state of the channel isverified using the signal to noise ratio.

For example, the minimum signal level at which the threshold signal tonoise ratio is exceeded is represented by the line 208. Thus, betweentimes T2 and T3, the channel over which the signal 202 is received isidentified as being in a permanent state because the signal level of thesignal 202 remains above the line 208. Accordingly, data received overthe channel can continue to be logged as valid data.

FIG. 3 is a flow chart of an example process 300 for determining whetherto store data received over a channel. The process 300 is a process bywhich signal levels of communications channels are monitored and adetermination is made that a signal level value for a particularcommunication channel is less than a threshold signal level value forthe channel. In response to the determination, a signal to noise ratiois computed for the channel and compared to a threshold value. When thesignal to noise ratio meets or exceeds the threshold value data receivedover the channel is stored as valid data. When the signal to noise ratiois less than the threshold value, the data is not stored as valid data.A notification that a capacitor bank has been activated can optionallybe provided when the signal level is less than the threshold signallevel and the signal to noise ratio is greater than the threshold value.

The process 300 can be implemented, for example, by the status subsystem114 and/or network management system 112 of FIG. 1. In someimplementations, the status subsystem 114 includes one or moreprocessors that are configured to perform the actions of the process300. In other implementations, a computer readable medium can includeinstructions that when executed by a computer cause the computer toperform actions of the process 300.

Signal characteristic values for communications channels of a power linecommunications system are monitored (302). In some implementations, thesignal characteristic values can be monitored for each channel of thenetwork. The signal characteristic values are values that represent thesignal and with which the signal can be characterized. The monitoredsignal characteristic values can include a signal level value forsignals transmitted over the channel and noise floor measures for thechannel. The signal characteristic values can be measured, for example,by a receiver device, signal measurement equipment such as anoscilloscope, spectrum analyzer (swept or real-time), or anothermeasurement device that is capable of measuring signal characteristicsover time. The measured signal characteristic values can be stored in adata store, such as the channel data store 116 of FIG. 1. The measuredsignal characteristic values can also be provided to a channelmonitoring device, such as the network management system 112 and/orstatus subsystem 114 of FIG. 1.

A determination is made that a signal level value for a channel is lessthan a threshold signal level value for the channel (304). Thedetermination can be made, for example, by comparing a currentlymonitored or received signal level value for the channel to thethreshold signal level value.

In some implementations, the threshold signal level value for thechannel is specified as a function of a baseline signal level for thechannel. For example, the threshold signal level for the channel can bespecified as a fraction of the baseline signal level (i.e., one-half orone-third of the baseline signal level) for the channel.

The threshold signal level value can be adjusted based oncharacteristics of the network in which the channel operates as well asreliability goals. For example, a higher threshold signal level valuecan be specified when data reliability is more important than thethreshold signal level value specified when data reliability is lessimportant.

The baseline signal level value represents the signal level value forthe channel under normal operating conditions. The baseline signal levelvalue can be computed, for example, based on signal level values thathave been measured for the channel over a specified time period. Forexample, the baseline signal level value for a channel can be an averageor median signal level value for the channel over a past week, month, oryear.

A signal to noise ratio is computed for the communications channel(306). The signal to noise ratio for the communications channel can becomputed, for example, based on the monitored signal level value and amonitored noise floor measures for the channel.

A determination is made whether the signal to noise ratio for thechannel is less than a threshold signal to noise ratio value (308). Thedetermination can be made, for example, by comparing the computed signalto noise ratio to a threshold signal to noise ratio that is stored in adata store or other memory structure.

In some implementations, the threshold signal to noise ratio for thechannel can be specified globally for all communications channels in thesystem. In other implementations, the signal to noise ratio for eachchannel can be determined on a per-channel basis.

The threshold signal to noise ratio can be selected, for example, basedon historical signal to noise ratio data that corresponds to datavalidity information. The data validity information can be any measureof data validity, such as a data valid bit that is included with eachreceived packet or a packet/bit-error-rate measurement.

The historical signal to noise ratio data can be analyzed to identify aminimum signal to noise ratio at which data received over thecommunications channels is valid with a threshold likelihood. Forexample, if a 99% likelihood of data validity is desired, the thresholdsignal to noise ratio can be selected as the signal to noise ratio atwhich 99% of received data is identified as valid based on the datavalidity information.

When the signal to noise ratio for the channel is not less than thethreshold value, data received over the channel is stored (310) andsignal characteristic values continue to be monitored (302).Additionally, the status of the channel can be maintained as, or changedto, “permanent state,” as an indication that data being received overthe channel is valid and that the channel is in a normal operatingcondition. The data received over the channel and the status of thechannel can be stored in a data store such as the channel data store 116of FIG. 1.

When the signal to noise ratio for the channel is greater than thethreshold signal to noise ratio and the signal level is less than thesignal level threshold, a notification that a capacitor bank has beenactivated can also optionally be provided (312). For example, a signalcan be generated that causes an LED to illuminate, a message to begenerated on a display device, an email or text message to betransmitted to a recipient, or any other form of notification to beprovided. The notification can be provided, for example to a powerprovider that manages the network, a maintenance staff, and/or acustomer service staff that receives calls from customers. Notificationthat a capacitor bank has been activated in the network can prevent anoperator from deploying repair crews to investigate whether a poweroutage has occurred.

When the signal to noise ratio for the channel is less than thethreshold signal to noise ratio, data received over the channel is notstored (314), and signal characteristic values continue to be monitored(302). Additionally, the status of the channel can be maintained as, orchanged to, “lost state,” (316) as an indication that data beingreceived over the channel is not valid and that the channel is not in anormal operating state. The status of the channel can be set to loststate in parallel with preventing data from being stored over thechannel. The status of the channel can also be set prior to or followingpreventing data from being stored over the channel. The status of thechannel can be stored in a data store such as the channel data store 116of FIG. 1.

FIG. 4 is block diagram of an example process 400 for identifyingactivation of a capacitor bank in a power distribution system. Theprocess 400 is a process by which signal characteristic values forsignals transmitted over communications channels are monitored. Usingthe monitored signal characteristic values, a determination is made thata capacitor bank has been activated in a power distribution system and anotification is provided that the capacitor bank has been activated.Optionally, a signal level of a channel can be determined to haveincreased above the threshold signal level for the channel. In turn, anotification can be provided that the capacitor bank has beendeactivated.

The process 400 can be implemented, for example, by the status subsystem114 and/or network management system 112 of FIG. 1. In someimplementations, the status subsystem 114 includes one or moreprocessors that are configured to perform the actions of the process400. In other implementations, a computer readable medium can includeinstructions that when executed by a computer cause the computer toperform actions of the process 400.

Signal characteristic values for signals being transmitted overcommunications channels of a power line communication system aremonitored (402). The power line communication system can be implementedin a power distribution system. The signal characteristic values foreach channel include a signal level value for the channel and a signalto noise ratio for the channel. The signal to noise ratio can bedirectly monitored or computed from the signal level value and a noisefloor measure for the channel.

Based on the monitored signal characteristic values, a determination ismade that a capacitor bank has been activated in the power distributionsystem (404). In some implementations, the determination is made bydetermining that the signal level value for a channel is less than athreshold signal level value and the signal to noise ratio for thechannel is greater than a threshold signal to noise ratio for thechannel.

Provide a notification that the capacitor bank has been activated (406).As described above with reference to FIG. 4, the notification can beprovided, for example to a power provider that manages the network, amaintenance staff, and/or a customer service staff that receives callsfrom customers.

A determination is made that the signal level value of the channel hasincreased above the threshold signal level (408). In someimplementations, the signal level value for the channel with which thecapacitor bank activation was identified can continue to be monitoredand compared to the threshold signal level value to determine whetherthe signal level value has increased to a value greater than thethreshold signal level value. When the signal level value of the channelincreases above the threshold signal level value, it is an indicationthat the capacitor bank has been deactivated.

A notification that the capacitor bank has been deactivated is provided(410). The notification can be, for example, a message indicating thatthe capacitor bank has been deactivated and presented on a displaydevice or another manner of indicating that the capacitor bank has beendeactivated.

FIG. 5 is a block diagram of an example computer system 500 that can beused to facilitate network event detection. The system 500 includes aprocessor 510, a memory 520, a storage device 530, and an input/outputdevice 540. Each of the components 510, 520, 530, and 540 can beinterconnected, for example, using a system bus 550. The processor 510is capable of processing instructions for execution within the system500. In one implementation, the processor 510 is a single-threadedprocessor. In another implementation, the processor 510 is amulti-threaded processor. The processor 510 is capable of processinginstructions stored in the memory 520 or on the storage device 530.

The memory 520 stores information within the system 500. In oneimplementation, the memory 520 is a computer-readable medium. In oneimplementation, the memory 520 is a volatile memory unit. In anotherimplementation, the memory 520 is a non-volatile memory unit.

The storage device 530 is capable of providing mass storage for thesystem 500. In one implementation, the storage device 530 is acomputer-readable medium. In various different implementations, thestorage device 530 can include, for example, a hard disk device, anoptical disk device, or some other large capacity storage device.

The input/output device 540 provides input/output operations for thesystem 500. In one implementation, the input/output device 540 caninclude one or more of a network interface device, e.g., an Ethernetcard, a serial communication device, e.g., and RS-232 port, and/or awireless interface device, e.g., and 802.11 card. In anotherimplementation, the input/output device can include driver devicesconfigured to receive input data and send output data to otherinput/output devices, e.g., keyboard, printer and display devices 560.Other implementations, however, can also be used, such as mobilecomputing devices, mobile communication devices, set-top box televisionclient devices, etc.

Although an example processing system has been described in FIG. 5,implementations of the subject matter and the functional operationsdescribed in this specification can be implemented in other types ofdigital electronic circuitry, or in computer software, firmware, orhardware, including the structures disclosed in this specification andtheir structural equivalents, or in combinations of one or more of them.

Implementations of the subject matter and the operations described inthis specification can be implemented in digital electronic circuitry,or in computer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them.

Implementations of the subject matter described in this specificationcan be implemented as one or more computer programs, i.e., one or moremodules of computer program instructions, encoded on computer storagemedium for execution by, or to control the operation of, data processingapparatus. Alternatively or in addition, the program instructions can beencoded on an artificially-generated propagated signal, e.g., amachine-generated electrical, optical, or electromagnetic signal, thatis generated to encode information for transmission to suitable receiverapparatus for execution by a data processing apparatus.

A computer storage medium can be, or be included in, a computer-readablestorage device, a computer-readable storage substrate, a random orserial access memory array or device, or a combination of one or more ofthem. Moreover, while a computer storage medium is not a propagatedsignal, a computer storage medium can be a source or destination ofcomputer program instructions encoded in an artificially-generatedpropagated signal. The computer storage medium can also be, or beincluded in, one or more separate physical components or media (e.g.,multiple CDs, disks, or other storage devices).

The operations described in this specification can be implemented asoperations performed by a data processing apparatus on data stored onone or more computer-readable storage devices or received from othersources.

The term “data processing apparatus” encompasses all kinds of apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, a system on a chip, or multipleones, or combinations, of the foregoing. The apparatus can includespecial purpose logic circuitry, e.g., an FPGA (field programmable gatearray) or an ASIC (application-specific integrated circuit). Theapparatus can also include, in addition to hardware, code that createsan execution environment for the computer program in question, e.g.,code that constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, a cross-platform runtimeenvironment, a virtual machine, or a combination of one or more of them.The apparatus and execution environment can realize various differentcomputing model infrastructures, such as web services, distributedcomputing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform actions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing actions in accordance with instructions andone or more memory devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto-optical disks, or optical disks.However, a computer need not have such devices. Moreover, a computer canbe embedded in another device, e.g., a mobile telephone, a personaldigital assistant (PDA), a mobile audio or video player, a game console,a Global Positioning System (GPS) receiver, or a portable storage device(e.g., a universal serial bus (USB) flash drive), to name just a few.Devices suitable for storing computer program instructions and datainclude all forms of non-volatile memory, media and memory devices,including by way of example semiconductor memory devices, e.g., EPROM,EEPROM, and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROMdisks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

To provide for interaction with a user, implementations of the subjectmatter described in this specification can be implemented on a computerhaving a display device, e.g., a CRT (cathode ray tube) or LCD (liquidcrystal display) monitor, for displaying information to the user and akeyboard and a pointing device, e.g., a mouse or a trackball, by whichthe user can provide input to the computer. Other kinds of devices canbe used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input. In addition, a computer can interact with a user bysending documents to and receiving documents from a device that is usedby the user; for example, by sending web pages to a web browser on auser's client device in response to requests received from the webbrowser.

Implementations of the subject matter described in this specificationcan be implemented in a computing system that includes a back-endcomponent, e.g., as a data server, or that includes a middlewarecomponent, e.g., an application server, or that includes a front-endcomponent, e.g., a client computer having a graphical user interface ora Web browser through which a user can interact with an implementationof the subject matter described in this specification, or anycombination of one or more such back-end, middleware, or front-endcomponents. The components of the system can be interconnected by anyform or medium of digital data communication, e.g., a communicationnetwork. Examples of communication networks include a local area network(“LAN”) and a wide area network (“WAN”), an inter-network (e.g., theInternet), and peer-to-peer networks (e.g., ad hoc peer-to-peernetworks).

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other. In someimplementations, a server transmits data (e.g., an HTML page) to aclient device (e.g., for purposes of displaying data to and receivinguser input from a user interacting with the client device). Datagenerated at the client device (e.g., a result of the user interaction)can be received from the client device at the server.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular implementations of particularinventions. Certain features that are described in this specification inthe context of separate implementations can also be implemented incombination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular implementations of the subject matter have beendescribed. Other implementations are within the scope of the followingclaims. In some cases, the actions recited in the claims can beperformed in a different order and still achieve desirable results. Inaddition, the processes depicted in the accompanying figures do notnecessarily require the particular order shown, or sequential order, toachieve desirable results. In certain implementations, multitasking andparallel processing may be advantageous.

1. A method performed by data processing apparatus, the methodcomprising: for each of a plurality of communications channels of apower line communications system implemented in a power distributionsystem: monitoring, by a data processing apparatus, signalcharacteristic values for signals transmitted over the channel;determining, by the data processing apparatus and based on the monitoredsignal characteristic values, that a signal level value for the channelis less than a threshold signal level value for the channel; in responseto determining that the signal level value for the channel is less thanthe threshold signal level value for the channel: computing, by the dataprocessing apparatus, a signal to noise ratio for the communicationschannel; determining, by the data processing apparatus, that the signalto noise ratio for the channel exceeds a threshold value; and inresponse to determining that the signal to noise ratio for thecommunications channel exceeds the threshold value, storing, by the dataprocessing apparatus, data received over the communications channel asvalid data.
 2. The method of claim 1, wherein monitoring signalcharacteristic values comprises monitoring signal level values and noisefloor measures for signals transmitted over the channel.
 3. The methodof claim 1, wherein determining that a signal level value for thechannel is less than a threshold signal level value comprises detectinga signal amplitude for signals transmitted over the channel that are atleast fifty percent less than a baseline signal level for the channel.4. The method of claim 1, further comprising: computing baseline signalcharacteristics for each of the communications channels, the baselinesignal characteristics representing normal operating characteristics forthe channels; and specifying the threshold signal level for the channelbased on a baseline signal level.
 5. The method of claim 4, whereincomputing baseline signal characteristics for each of the communicationschannels comprises computing, for each of the communications channels, abaseline signal level of the channel based on signal level values thathave been measured for the channel over a specified time.
 6. The methodof claim 1, wherein monitoring signal characteristic values for signalstransmitted over the channel comprises monitoring signal characteristicvalues for a signals transmitted over a channel of a power linecommunications system.
 7. The method of claim 1, further comprising: inresponse to determining that the signal level value for the channel isless than the threshold signal level value and that the signal to noiseratio for the channel is greater than the threshold signal to noiseratio: determining that a capacitor bank has been activated in the powerdistribution system; and providing a notification that the capacitorbank has been activated in the power line distribution system.
 8. Acomputer-implemented method, comprising: for each of a plurality ofcommunications channels of a power line communications systemimplemented in a power distribution system: monitoring, by a dataprocessing apparatus, signal characteristic values for signalstransmitted over the channel; determining, by the data processingapparatus and based on the monitored signal characteristic values, thata signal level value for the channel is less than a threshold signallevel value for the channel; computing, by the data processingapparatus, a signal to noise ratio for the communications channel;determining, by the data processing apparatus, whether the signal tonoise ratio for the channel is less than a threshold value; in responseto determining that the signal to noise ratio for the communicationschannel is less than the threshold value, preventing, by the dataprocessing apparatus, storage of data received over the communicationschannel as valid data; and in response to determining that the signal tonoise ratio for the communications channel is not less than thethreshold value, storing, by the data processing apparatus, datareceived over the communications channel as valid data.
 9. A computerstorage medium encoded with a computer program, the program comprisinginstructions that when executed by data processing apparatus cause thedata processing apparatus to perform operations comprising: for each ofa plurality of communications channels of a power line communicationssystem implemented in a power distribution system: monitoring, by a dataprocessing apparatus, signal characteristic values for signalstransmitted over the channel; determining, by the data processingapparatus and based on the monitored signal characteristic values, thata signal level value for the channel is less than a threshold signallevel value for the channel; in response to determining that the signallevel value for the channel is less than the threshold signal levelvalue for the channel: computing, by the data processing apparatus, asignal to noise ratio for the communications channel; determining, bythe data processing apparatus, whether the signal to noise ratio for thechannel is less than a threshold value; in response to determining thatthe signal to noise ratio for the communications channel is less thanthe threshold value, preventing, by the data processing apparatus,storage of data received over the communications channel as valid data;and in response to determining that the signal to noise ratio for thecommunications channel is not less than the threshold value, storing, bythe data processing apparatus, data received over the communicationschannel as valid data.
 10. A system, comprising: a data store storingchannel characteristics for a plurality of communications channels of apower line communications system, the channel characteristics includingsignal level measurements and noise floor measurements for the channelsover one or more specified time periods; and a status subsystem coupledto the data store, the status subsystem including one or more processorsconfigured to determine whether to store data received over each of thechannels of the power line communications system, the determination foreach channel being based on a signal level value for the channel and asignal to noise ratio for the channel.
 11. The system of claim 10,wherein the status subsystem is operable to compute a baseline signallevel for each channel and specify a threshold signal level value foreach channel based on the baseline signal level for the channel.
 12. Thesystem of claim 11, wherein the status subsystem is operable to monitora signal level value for a channel and determine that the monitoredsignal level value for the channel is less than the threshold signallevel value for the channel.
 13. The system of claim 12, wherein thestatus subsystem is operable to determine that the signal to noise ratiofor the channel is greater than a threshold signal to noise ratio andcause data received over the channel to be stored as valid data.
 14. Thesystem of claim 13, wherein the status subsystem is operable to generatea notification that a capacitor bank has been activated in response tothe determination that the signal level for the channel is less than thethreshold signal level for the channel and the determination that thesignal to noise ratio for the channel is greater than the thresholdsignal to noise ratio for the channel.
 15. The system of claim 14,wherein the status subsystem is operable to determine that the signal tonoise ratio for the channel is less than a threshold signal to noiseratio and prevent data received over the channel from being stored asvalid data.
 16. The system of claim 12, wherein the status subsystem isoperable to specify the threshold signal level value for a channel basedon signal level values for the channel that have been measured over aspecified time.
 17. A computer-implemented method, comprising: for eachof a plurality of communications channels of a power line communicationsystem implemented in a power distribution system: monitoring, by a dataprocessing apparatus, signal characteristic values for signalstransmitted over the channel of the power line communications system;determining, by the data processing apparatus and based on the monitoredsignal characteristic values, that a capacitor bank has been activatedin the power distribution system based on a signal level value for thechannel being less than a threshold signal level value for the channeland the signal to noise ratio for the channel being greater than athreshold signal to noise ratio for the channel; and providing anotification that the capacitor bank has been activated.
 18. The methodof claim 17, further comprising: determining that the signal level valueof the channel increases above the threshold signal level value for thechannel; and providing a notification that the capacitor bank has beendeactivated.